The distribution patterns of the sediment and various characteristics in Apalachicola Bay and vicinity are clearly defined and greatly influenced by the submarine topography. Analysis shows a variability in the mean grain size and in the carbonate content between the basins and the shoals. The coarse fractions of the sediments consists of reworked relict quartz sands with negligible percentages of heavy mineral or calcareous material indigenous to the area. This course material is associated with topographic elevations, channel floors, and the most distant shelf areas. Distribution of the fine-grained sediment is related directly to the submarine physiography, which is essentially formed from the coarse sediments in the area. The bays, shoals, and intervening depressions inhibit the migration of the sediment by forming natural traps. In addition, these features cause a dissipation of the wave energy. All the fine-grained sediment in the area can be attributed to the Apalachicola River; the bulk of it is contained in Apalachicola Bay proper. The distribution of the mean grain size, the organic C content, and the standard-deviation patterns closely approximate the configuration of the bottom topography. The regional and residual aspects of these characteristics are also closely related.